Hatch cover having pairs of folding covers

ABSTRACT

A hatch cover of the kind in which at least two pairs of hinged covers are connected together for articulation, one end cover being articulated to an end of the hatch so that the covers are foldable in a zig-zig manner from a closed position in which they lie flat on the sill of the hatch to a fully open position in which they are folded together and extend upright from the sill. Adjacent pairs of covers are articulated by a drive mechanism including a crank engaged by an actuating piston and a link pivotally connected at one end to the crank and to one of two adjacent covers and at the other end to the other of the adjacent covers to allow the covers to be swivelled through an included angle of 180*. The lever arm of the crank between the line of action of the piston and the point of articulation of the crank with said one cover is shorter than the lever arm between the point of articulation of the crank with said one cover and a second link by which the crank is connected to the other cover in the fully extended positions of the covers, thereby enabling the pair of covers nearer to the end of the hatch to which the end cover is articulated to be fully folded while the next pair of covers is held fully open.

United States Patent 1191 Kloess et a].

[ Mar. 5, 1974- l HATCH COVER HAVING PAIRS OF FOLDING COVERS 22 Filed: Aug. 3, 1972 1211' Appl. No.: 277,583

[30] Foreign Application Priority Data Aug. 4, 1971 Germany .l. 2139020 52 US. Cl. 114/202,160/188 [51] Int. Cl.. B63b 19/20 [58] Field of Search 114/202, 201 R, 203; 160/188; 5 I I .1 74/110 [56] References Cited UNITEDSTATES PATENTS 3,104,643 9/1963 Vallet 114 202 3,113,613 12 1963 Hamilton 160 188 3,180,302 4 1965 1161111116 160 188 3,220,467 11 1965 Harnilton.. 160 18 3,326,169 6/1967 B038 -1 14 202 3,335,783 8/1967 Ligh 160/188 3,369,590 2/1968 OlSSOll 160 188 FOREIGN PATENTS OR APPLICATIONS 3/1960 Australia 114/202 Primary Examiner-George E. A. Halvosa Assistant Examiner-Edward R. Kaze'nske Attorney, Agent, or F i'rm salter 8L Michaelson 57] ABSTRACT A hatch cover of the kind in which at least two pairs of hinged covers are connected together for articulation, one end cover being articulated to an end of the hatch so that the covers are foldable in a zig-zig manner from a closed position in which they lie flat on the sill of the hatch to a fully open position in which they are folded together and extend upn'ght from the sill. Adjacent pairs of covers are articulated by a drive mechanism including a crank engaged by an actuating piston and a link pivotally connected at one end to the crank and to one of two adjacent covers and at the other end to the other of the adjacent covers to allow the covers to be swivelled through anincludedangle of 180 The lever arm of the crank between the line of action of the piston and the point of articulation of the crank with said one cover is shorter than the lever arm betweenthe point of articulation ofthe crank with said one cover and a second link by which the crank is connected to the other cover in the fully extended positions of the covers, thereby enabling the pair of covers nearer to the end of the hatch to which the end cover is articulated to'be fully folded while the next pair of covers is held fully open.

20 Claims, 14 Drawing Figures PAIENTEUHAR 51914 I 3.795217 22 12v 22 20 10 fig] PATENTEU 51974 SHEET 2 HF 5 EDIT Mid/.4

PATENTEB MAR 5 I974 SHEET 3 BF 5 HATCH COVER HAVING PAIRS OF FOLDING COVERS 1 The invention concerns a hatch cover including a pair of folding'covers to be articulated to the hatch adjacent one end thereof, at least one further pair of folding covers articulated to the first pair, a four-link drive mechanism interconnecting adjacent covers of adjacent pairs of said folding covers and a piston device mounted to operate the drive mechanism to effect swivclling between said two adjacent covers, the drive mechanism comprising a crank engaged by said piston device and pivotally mounted on one of said adjacent nected between said crank at a point spaced from the point of its articulation to said one cover and said other cover at a point spaced from the point of its articulation to said first link. i i i Hatch covers of this type have'the advantage that only a single drive mechanism or a single pair of drive mechanisms need to be provided, respectively, for two pairs of folding covers. 1 In a known hatch cover of the foregoing type, the drive mechanism is constructed in such a way that, during opening, the second pair of folding covers (i.e., the pair further from the end of the hatch to which the cover is articulated) is first folded-up into a vertical position. -The first pairof folded covers is only folded after the second pair of folding covers has attained its folded position and it .thus drags the second pair of covers after it. On, closing the hatch, the first pair of folded covers closesfirst and thus the second pair of folding covers are pushed away in the folded position, In open ing and closing movements of this kindthe second pair of covers is.in an unstable position. It is also a disadvantage in the practical use of a hatch cover of the foregoing type that forces which, for instance, act on the second cover of the second pair of covers make themselves felt in'the whole system of forces as forcesof reaction. I v C An object of the invention is to design a hatch cover of the type described, which will operate without instability and in which the stability of the covers during folding-up and unfolding is not impaired by external forces, as, for instance, produced by obstacles on the sill of the hatch.

According to the invention, the drive mechanism of the hatch cover is such that a first lever arm of the crank between the line of action of the piston device and the point of articulation of the crank with said one cover is shorter than asecond lever arm between said point of articulation of the crank-withsaid one cover and said second link when the covers are in their fully- I means also being provided on said other cover of the adjacent pair of folding covers to render said holding means inoperable when the other pair of said folding covers, that is the pair further from said one end of the hatch has been closed.

In the realisation of the object according to the invention, it is ensured, by the choice of the effective lever arms of the drive mechanism in the extended position of the covers, that the force of reaction is large enough on the first pair of folding covers as to cause this pair of covers to be folded up, at the same time pulling after it the second pair of folding covers, while the force of reaction on the second pair of folding covers is so small that it is not sufficientto initiate the folding movement of the second pair of folding covers. By the means according to the invention, in which the second pair of folding covers is held in the extended position until the first pair of folding covers has reached its folded position, the hatch cover is protected against the situation in which the second pair of folding covers is folded-up, while the first pair of folding covers prevents or interrupts the initiation of the folding-up process of the first pair of folding covers owingtoan obstacle, for instance a fallen load, or an obstacle on the running rail which hinders rolling. Finally, the holding means which is automatically put into effect or out of action, ensures that the first pairof folding covers is unable to change its folded position during the foldi'ng-upof the second pair of folding covers. At the same time it is ensured that, the second pair of folding covers must have adopted a fully folded position before the first pair of folding covers can begin the unfolding movement. in this way it is made impossible for,'for-instance, the unfolding movement of the second pair of folding covers to be hindered by an obstacle on the running track and this pair of folding covers to' be subsequently overturned by the unintentional unfolding movement of the first pair of folding covers.

The second cover of the first pair of folding covers (i.e., said one cover of said adjacent covers) preferably has a swivclling pawl close to the joint which connects it to the first cover of the second pair of folding covers (i.e., said other cover 'ofsaid adjacent covers), and'a fixed stop is provided on the sill of the hatch behind which fixed stop the pawl engages when the pair of folding covers nearer to said one end of the hatch has been fully folded. The pawl is preferably spring-loaded, which may, for instance, be achieved by providinga rubber torsion spring as a mounting for the pawl.

A release lever is conveniently arranged on said other cover of said adjacent covers and works in conjunction with the holding means on said one cover of said adjacent covers. The release lever is preferably mounted so that it can swivel and work in conjunction with a stop on the cover which carries it, the stop acting to limit its downward swivclling movement. The release lever is preferably spring-loaded. Spring-loading can be achieved by providing a rubber torsion spring. as a mounting. 1 I

In a preferred form of embodiment, a swivclling pawl is arranged on said one cover of said adjacent covers adjacent the point of articulation thereon of the crank, which engages behind a stop mounted in a fixed position on the sill of the hatch and a release lever is arranged on said other cover of said adjacent covers and works in conjunction with the pawl in such a way that on the closure of this cover to the end of its closing path the pawl is brought out of its engagement with the fixed stop.

In a particularly convenient form of embodiment, said first link, which connects the two pairs of folding covers together, is arranged adjacent the side edges of the hatch cover, and two bogie wheels are arranged on the drive mechanism, so that they run on a runway on the edge of the sill of the hatch and are separated by a distance greater than the distance between the points of articulations of the hinged joint. A swivelling pawl, which, in the folded position of thepair of folding covers nearer to said one end of the hatch engages with a stop on the sill of the hatch is conveniently mounted in bearings on the first link which also serves as a means of carrying-out the covering of the hatch.

In order to achieve the differing forces of reaction of the drive on each of the two folding pairs, as described above, the ratio of the said first and second lever arms is selected to Eabout lzZ in the extended position of the pairs of folding covers.

In order to hold down the second pair of folding covers at the beginning of the opening movement, said one cover of said adjacent covers can be provided with rollers on its outer side, placed at a distance from the coupling to said other cover of said adjacent covers, the said rollers being supported against the underside of guide rails attached to the sill of the hatch, which end at a distance from the articulation of the pair of foldingcovers nearer to said one end of the hatch in such a way that the rollers are freed from the guide rails when the first pair (i.e., the pair nearer to said one end of the hatch) of folding covers reaches its fully-folded position. The ends of the guide rails facing towards the articulation with the first pair of folding covers with the sill of the hatch are conveniently, provided with an up ward slope. Alternatively, a roller operating to hold down said other cover of said adjacent covers can be provided on the sill of the hatch in the region in which that cover lies in the closed position.

As a further possibility for holding down the pair of folding covers further from said one end of the hatch, a hydraulically-operated means of bolting can be provided in the region of the folding hinges of said further pair of folding covers, the said means being able to be operated in conjunction with the folding movement of the pair of folding covers nearer to said one end of the hatch. t I

The invention is illustrated by examples in the drawing and with described, with8c further details, in the following.

FIG. 1 shows, in a schematic side view, a hatch cover with two pairs of folding covers, linked together according to the invention, in their closed position;

FIG. 2 shows the hatch cover of FIG. 1 during the folding-up of the first pair of folding covers;

FIG. 3 shows the hatch cover in the open position;

FIG. 4 shows, in an enlarged representation, a swivel drive in the form of a four-linktransmission, in the closed position of the hatch cover;

FIG. 5 shows the swivel drive of FIG. 4 after completion of the folding of the first pair of covers;

FIG. 6 shows the swivel drive with the hatch cover completely open; I

FIG. 7 shows the hydraulic control system of a hatch cover according to the invention, in a realisation form with hydraulically operated bolts;

FIG. 8 shows a section along the line VIIIVIII of FIG. 4;

FIG. 9 shows a section along the line IXIX of FIG.

FIG. 10 shows the operation of the swivel drive by means of a torque diagram;

FIG. 11 shows an automatic bolting device for th first pair of folding covers with a different arrangement of the articulated link between the neighbouring covers;

FIG. 12 shows the device of FIG. II in the open position;

FIG. 13 shows a section along tbe line A-B in FIG. 11, and

FIG. 14 is a section along the line C-D of FIG. 11.

The hatch cover, as illustrated in FIG. 1, is of the usual design in its basic construction. It contains two pairs of folding coversjoined together flexibly. The first pair of folding covers, comprising the covers 1 and 2, is joined together by means of the articulated joint 3 lying onthe underside of the covers. The cover 1 is articulated by means of an articulation 4, to a fixed point at the end of the sill of the hatch 6. The second pair of folding covers, comprising the covers 8 and 10, joined together by an articulated joint similar to joint 3 is linked to the pair of covers 1 and 2 by means of a hinged shackle 12 with articulations l4 and 16. The articulation 14 is on the cover 2 and articulation 16 on cover 8. A swivel drive 20, activated by a hydraulic thrust piston drive 18, is arranged at the link between the two pairs of covers, and is so designed as to be able to swivel the covers 2 and 8 through relative to each other.

Further details of the drive are described with reference to FIGS. 4 to 6.

The pairs of folding covers are provided with rollers in the usual manner. A roller is attached to the end of cover 2 which faces the articulation 4. This roller 22 runs in bearings, in the usual manner, onan arm projecting over the end of the cover. The cover 10 is provided with two pairs of bogie wheels 24. The bogie wheels lie on the runway 26, which stretches in the Ion gitudinal direction along the edge of the sill. The hatch covers can be lifted off the sill or lowered down on to the sill, in the usual manner.

A roller 28 rotates in bearings on the hatch cover 8 at a distance from the hingedshackle 12. The roller 28 runs along a guide track 30 fastened to the sill and, in the raised position of the cover, lies on the underside of this guide track.

Although, as will be further described in the following description, the swivel drive can be so designed that the first pair of folding covers are positively folded up, it may be necessary to provide additional means for ensuring the termination of the movement. The roller 28 and the guide track 30, as will be seen from the following description, exert a control on the folding sequence. On opening the hatch cover, one force of reaction due to the swivel drive 20 acts on the cover 2 and the other force of reaction on cover 8. The force of reaction operating on the cover 8 is further conveyed through roller 28 to the guide track 30. Thus it results only in a swivelling movement of the cover 2 and thus a folding movement of the first pair of covers articulated to the sill. During this folding-up process, the second pair of folding covers is pulled in its extended position over the hatch in the direction of the end sill 6 of the hatch. The guide track 30 stretches sufficiently far in the direction of the articulation 4 to ensure that the roller 28 is freed from the guide track 30 when the first pair of folding covers has reached its fully folded position. From the instant at which the roller 28 is freed from the track 30, the moment of reaction can act, in the sense of a folding movement on the second pair of folding covers which is thus brought into. the fully folded position, as is shown in FIG.' 3, through the further working path of the swivel drive.

The construction illustrated in FIGS. 1 to 3 is especially suitable for surface deck hatches where the guide track 30 can easily be mounted on thesides of the sill opening.

It may be convenient to provide a slope 32 directed upwards at the end of the guide track 30 nearer to the end 6 of the sill. By means of this slope 32 a component first release the roller 28 when 'the first pair of folding covers has reached its fully foldedposition. Since the torque necessary for the folding of the pair of covers decreases with increasing angle of folding, the-roller 28 could, for example, be'released as early as a folding movement of 90 by the first pair of folding covers, that is at'the partly folded positionshown in FIG. 2, since at this time the torque generated ,by the swivel drive would first take effect in further.'folding of the first pair of folding covers and the folding of the second pair of foldingcovers would only start after the fully.folded p0.-

sitionhas been reached. A similar effect'could also be achieved by designing the second pair of covers to have a somewhat greater length of cover, so that, from the beginning, a smaller torque would be necessary for the folding of the first pair of folding covers.

In an alternative construction rollers to hold down the covers could be attached to the sill of the hatch, so that these rollers could either work in conjunction with corresponding ledges on the sides'of the hatch cover or otherwise operate on the upper side of the hatch cover. In the latter case the rollers holding down the covers could also be movable between an inoperative position in which they are 'ineffective and their effective position.- 1

FIGS. 4 to 6 and 9 illustrate the adjoining ends of the covers 2 and 8, which are linked to each other by the tion with a stop-11 on the cover 2 and prevents a swivelling movementof the hinged shackle in a clockwise direction aboutthe swivellingarticulation 14. A further stop face 13 on the hinged shackle 12 works in conjunction with .a stop face. 15 to limit the swivelling movement of thehinged shackle 12 about the swivel axis 14 in the anticlockwise direction, that is out of the plane of the covers when flat in their closed positions. A stop face 17 on cover 8 limits the clockwise swivelling movement of the hinged shackle 12 about the swivelling articulation 16. The hinged shackle impinges with its upper edge as'stop face on this stop 17. A main link 34, acting as crank, in the four-link swivel-drive is articulated on the cover 2, coaxial with the swivelling articulation 14 of the hinged shackle 12. The thrust piston drive 18 acts on this main link at the swivelling articulation 44, which is indicated in FIGS. 4 to 6 only by its bearing eye 46. The three articulation points 14, 38, and 44 are arranged superficially at a distance from each other on the main link. In between deck hatches this main link can be designed in the form of a triangu lar plate. In this case incisions must be provided in the covers 2 and 8 to allow for the overlapping of this plate. In the construction illustrated, which has a groove packing, the main link 34 has an indentation 36 to accept the packing arrangement and the ends of the covers. The main link 34 is attached to the intermediate link 40, acting as transmission coupling, by the swivelling articulation 38, and, in its turn, the intermediate link 40 is articulated with the cover 8 by means of a swivelling articulation 42 at a distance from the articulation 16. The four-link transmission 20 consists of the main link 34, the intermediate link 40', the hinged shackle 12, which may be regarded as part of the cover 2, and the fixed-link plate 48 at the end of the cover between the articulations 16 and 42. In use, a torque can be transmitted through the mainlink 34, acting as crank, which is determined by the pressure applied by the thrust piston drive'and the distance between the line of application of the forceand the articulation 14, lever arm 1,. The intermediate link 40 acts as a coupling and can thus transmit forces only in the line joining its two hinge axes. The lever arm 1 corresponds to the perpendicular from articulation 14 'on to this line. The pressure force conducted through the intermediate link 40 to the flange of cover 8 also produces a torque whichv is ,determinbd by the product of this force and the lever arm about the articulation 16. The lever arms 1,, l and 1 are shown in FIG. 4. As can be seen from the foregoing, the torque acting on the cover 8 is small in relation to the acting moment on cover 2 as' long as the lever arm 1 is small in relation to the lever arm 1 and the lever arm is againtsmaller than the lever arm 1 Thus it is possible, by a correct choice of the effective lengths of the lever arms, and, therefore by means of the configuration of the four-link transmission, to achieve the desired control of the sequence of operations in such a way that the pair of folding covers 1, 2 articulated at 4 near to the end sill 6 of the hatch are folded up first.

Thus, a moment P X 1, acts on the first folding pair, while a moment P X I l /l acts on the second folding pair or on a single adjacent cover. For with a link ratio 1 :1 :1 l:2:l the moments calculated for the first and second folding pairs are plotted in FIG. 10. The moments at the covers necessary forthe folding-up are also shown in the diagram. The individual curves thus show thatthe first folding pair will be completely folded-up before the folding movement begins forthe second folding pair.

The effect described above occurs as long as no external forces act on the cover. If the first pair of covers is prevented from folding-up by an effect from the outside, for instance by a load resting on .it, then the second pair of folding covers would tend to be folded-up by the drive. Such a folding-up movement of the second pair of folding covers, before the first pair of folding covers has reached its fully folded position, must be prevented in all cases. This is brought about by the holding down of the second pair of folding covers by the holding-down rollers described above. A hydraulic bolting device, to be described later, could also be used for this purpose.

FIG. 4 shows the four-link transmission in the position of closed covers. As can be seen from FIG. 9 in this position the stop face 9 of the hinged shackle 12 rests against the stop 11 on the cover 2, so that the cover 8 cannotfall awa'y even when the thrust piston drive is released. On reaching the fully folded-up position of the first pair of folding covers the stop face 13 of the hinged shackle 12 rests against the stop face 15 under the force transmittedthrough the hinged shackle, so that by the completion of the folding-up movement of the second pair of folding covers the articulation 16 on the cover 8 is fixed. When the folded-up position of the second pair of covers, as illustrated in FIG. 6, has been reached, the stop face 17, attached to the cover 8, rests against the upper side of the hinged shackle 12, so that a swivclling movement of the hinged shackle relative to the cover 8 is prevented. Thus, even with released gears, that is after removing the thrust piston drive, there is no swivellingmovement of the hinged shackle about the articulation 14 and thus the covers remain stationary at a predetermined distance from each other. e 7

It is also possible, in cases where a hinge protruding from the plane of a cover does not cause interference, to connect the two covers of a pair directly together with an inflexible hinge instead of with the hinged shackle as illustrated. The described action of the transmission linkage will not be altered thereby with respect to the sequence of the folding-up movement.

. Four-link transmissions of the type described hereinbefore have only been used, up to the present, for folding drives where the folding articulation lies a considerabledistance below the planes of the covers of articulated pairs of coversand easy mounting of sealing between the adjacent covers of the articulated pairs of covers packing is possible. As can be seen from FIG. 4, the mounting of packing 52 is possible with the transmission assembly according to the invention. Here, a packaging carrier is not engaged by the main link 34, even in the fully folded position, as shown in FIG. 6. In the construction provided with packing it is, however, necessary to arrange the hinged'shackle 12 at the side at a distance from the swivel transmission. An example of such a construction is shown in FIG. 8. Here the swivel transmission lies to one side ata distance from the two hinged shackles 12, which are supported on the two ends of the cover by their two hinge bolts 14 or 16 in welded-in supporting levers 50. In the vicinity of the hinged shackles the packing carrier 52 is carried downwards under the hinged shackles and from there it runs in the same plane to the edges of the covers so that the joint space can be drained from the outside. In this case, the hinged shackle will be exposed to atmosphere. The individual bearing positions could, however, easily be encapsulated in a water-tight manner by packings between the .hingcd shackle l2 and the supporting plates and by providing a cover over the ends of the hinge bolts. If more than one swivel drive is necessary for the covers, the pocket lying between the swivel drives could easily be connected, above the packing, by a draining conduit running through the ends of the covers to the joint space lying on the outside of the covers.

Some means of controlling the sequence of operations duringthe opening of the hatch cover have already been described in the foregoing a further embodiment of such. a control of the sequence of operations is illustrated in FIG. 7. In this Figure only those parts of the mechanical system which are necessary for its understanding are illustrated. Here, a bolting wedge 60 is attached to the underside of the cover 2. The bolt is operated by a thrust piston drive 64. It operates with a bolt acceptor 66 fastened to the underside of the cover 1. In a similar manner a bolt 70 is mounted on the underside of the cover 8 and is operated by a thrust piston drive 74 and operates in conjunction with a bolt acceptor 76 attached to the cover 10 which aligns with the bolt when the covers lie in the extended position. On the other hand, the bolt acceptor 66 aligns with the bolt 60 when the covers 1 and 2 lie with their undersides together in the fully folded-up position. The swivel drive is only shown schematically by its piston thrust drive 80, attached to the underside of the cover 2. On the piston side of the piston thrust drive, hydraulic fluid is delivered to a conduit 82, in which a controllable check valve 84 is mounted. The rod side is connected with a pressure limiter, connected in parallel, through a conduit 86 with a check valve effective in the direction towards the rod space. A hydraulic endswitch 68, with a blocked and an open position, is mounted on the underside of cover 2 and is moved from the blocked position into the operative position when the cover 2 and the cover 1 are fully folded together. One connection of the switch 68 leads to the conduit 82. A conduit 90 leads from the other connection to the piston rod side of the thrust piston drive 74 which is effective in unbolting. A conduit 92, with a check valve effective in the direction towards conduit 90, also leads from conduit 90 to the piston rod side of the thrust piston drive 64, operative in bolting, which is further connected, through a conduit 94, with a I check valve effective towards the piston side, to the conduit 82. The rod side of the thrust piston drive, operative in unbolting, is connected through a conduit 96 with the piston side of the thrust piston drive 74 and a conduit 97, in which there is a check valve effective in the direction towards the conduit 102. The conduit 96 is connected to the conduit 86 through a conduit 98, with a check valve 100 which can be unclosed by pressure in the conduit 90. A hydraulic end-switch 104 in a conduit ,102 lies in parallel with the conduit 97 and is mounted on the underside of the cover 8 and works in conjunction with the cover 10 in such a way that, when the pair of covers 8 and 10 are extended, that is in the open position, and moves into the closed position immediately at the beginning of the folding process of the two covers.

. The circuit described operates in the following manner. With closed hatch covers, the bolting wedge 70 is in effective engagement with the bolt acceptor 76, so that the covers 8 and 10 are bolted against folding. The bolt 60 is in its inoperative position. Passage through the end-switch 68 is blocked, passage through the endswitch 104 is open. lfthe hydraulic fluid enters the system through input I, only the piston side of the piston thrust drive 80 is operated initially. Since the two covers 8 and 10 are bolted against swivclling movement, the cover pair with the covers 1 and 2 is folded up. When these two covers come together with their undersides incontact, the switch 68 is switched to the open position. Thereby, the piston side of the piston thrust drive 64 receives hydraulic fluid so that the bolt 60 engages with the bolt acceptor 66 and the two covers are bolted together. At the same time the piston side of the piston thrust drive 74 receives hydraulic fluid, so that the bolt 70 is disengaged from the bolt acceptor 76 and folded first. Immediately before they reach the extended position, the switch 104 switc,hes to the open position so that hydraulic fluid then reaches the thrust piston drives 64 and 74, which bring the bolt 70 onto its bolting position and the bolt 60 out of engagement with the bolt acceptor 66. The back flow of fluid forced out of the thrust piston drives ,64 and 74 is able to flow away through the check valve into conduit 92 and through the check valve into conduit 94 and into conduit 82. The check valve 84 is closed by ,the pressure in conduit 86. The switch 68 closes immediately after the beginning of the folding movement of the covers 1 and 2. I

In the construction according to FIGS. 11 to 14, the two adjacent covers 2 and 8 of the two pairs of folding covers are linked together by the hinged link 110 by means of the'articulations l4 and'16, which are arranged respectively at the sides on'the outside of the hatch cover. Bogie wheels 22, 24 are arranged at a dis- 1 tance from each other on hinged link 1 10, at a distance apart which is greater than the d'istanc'ebetweenthe articulations 14 and 16, and are displaced, respectively, to the front or the rear of the articulations 14*and 16.

The hinged links 110 are thus designed as vva type ofundercarriage, by which the rocking movement exerted during openingand closing can be absorbed. The articulations l4 and 16 are here aligned with the articulations 14 and 16 of the other hinged shacklemoun'ted in the cover. 1

A pawl 111, with an articulation 112, is mounted in bearings on the hinged link, 110, and is able to swivel up and down and, as FIG. 12 shows, operates in con junction with a stop 114 on the sill of the hatch. The downward swivelling movement, that is a clockwise swivelling movement in the drawing,.is'limited'by a stop 113 on the hingedlink 1 10. Thepawl 111 is, preferably, urged in'the clockwisedirection by means 'of a spring 118, which isshown in FIG. .12 as a wire torsion spring. A rubber torsion spring could,1howev er, be used as a means of preloading andattached by its inner bush to the linking pin 112. A rubber torsion springof this type has the advantagethat no running surfaces which may tend to become dirty or iced have to be provided. Thepawl 111 has a stop nose 111a andarelease nose ll lb. The release riose operates in conjunction with a release lever which is attached to the cover'8. This release lever is attached tothe cover 8 by means of an arm 116 with a hinge 119. The release lever 117 is attached at the top, so that it is able to swivel, to the arm 116 by means of the hinge 119. A downward swivelling movement of the release lever is limited by striking against the arm l16.The-release lever 117 is also preferablyspri'ng-loaded. Once again this can be brought about by providing the link connection 119 with a rub ber torsion springnThe release lever 1.17 may, however,

also be connected to the arm 116 through a simple plate-shaped rubber element or a flexible metal element.

The manner of operation of the bolting device illustrated in FIGS. 11 to 14 now follows. When the first pair of covers swivel upwards the pawl with its stop nose 111a resting on the sill is swivelled about the articulation 112. When the fully folded position of the first pair of covers is reached the pawl falls with its stop nose 111a behind a stop 114. Thus the first pair of folding covers is secured against unfolding. When the second pair of. folding covers folds up, the release lever 117 strikes on the release nose lllb. On account of the link connection 112 the release lever ean, however, move past the release nose. When the second pair of folding covers are folded up, the release lever assumes the position shown in FIG. 12. When the hatch cover is closed, the release lever, after extensive unfolding of the second pair of folding covers, impinges on the underside of the release nose lllb and then, as unfolding of the second pair of folding covers proceeds further, swivels the pawl 111 in an anticlockwise direction (with reference to FIG. 11) so that the stop nose is disengaged from the stop 114 and the first pair of covers can then also proceed'with the unfolding movement. The movement of the pawl during the closing of the hatch cover is shown in two positions by dotted lines in FIG. 11. The length of the release nose lllb is so chosen that the release lever 117 moves past the release nose at the end of the closing movement and the pawl is, thus, under the influence of its spring-loading brought into position with the stop nose 111a resting on the sill.

adjacent covers, the drive mechanism comprising a crank engaged by said piston device and pivotally mounted on one of said adjacent covers, a first link pivotally connected between the crank at the point of its articulation with said one cover and the other cover of said adjacent covers, thereby to allow said adjacent covers to be swivelled through an included angle of and a' second link pivotally connected between said crank at a point spaced from the point of its articulation to said one cover and said other cover at a point spaced from the point of its articulation to said first link, afirst lever arm of the crank between the line of action of the piston device and the pointof articulation of the crank with said one cover. being shorter thana second lever arm between saidpoint of articulation of the crank with said one cover and said second link when the covers are in their fully-extended positionsin which the included angle between saidadjacent covers is 180.

2. A hatch cover claimed in claim 1 in which means are provided on said one cover of the adjacent pair co-operable with a stationary ,part of the hatch to hold the pair of folding covers nearer to said oneend of the hatch in its folded position, and release means are provided on said other cover of the adjacent pair to 11 render said holding means inoperable when the other pair of said folding covers, that is the pair further from said one end of the hatch has been closed.

3. A hatch cover as claimed in claim 2 in which a swivelling pawl is mounted on said one cover of said adjacent covers adjacent tbe point of articulation thereon of the crank and that a fixed stop is provided on the sill of the hatch, behind which fixed stop the pawl engages when the pair of folding covers nearer to said one end of the hatch has been fully folded.

4. A hatch cover as claimed in claim 2 in which a release lever is mounted on. said other cover of said adjacent covers and works in conjunction with the holding meanson said one cover of said adjacent covers.

5. A hatch cover as claimed in claim 4 in which the release lever is able to swivel in bearings and works in conjunction with a stop on the cover carrying it which jacent covers adjacent the point of articulation thereon of the crank which engages behind a stop mounted in a fixed position on the sill of the hatch, and a release lever is mounted on said other cover of said adjacent covers and works in conjunction with the pawl in such a way that on the closure of this cover tothe end of its closure path, the pawl is brought out of its engagement with said fixed stop.

7. Ahatch cover as claimed in claim 1 in which said first link is mounted adjacent the side edes of the hatch cover, and two bogie wheels are mounted on the drive mechanism and rest on a runway on the edge of the sill of the hatch, the distance apart of said wheels being greater than the distance apartof the two points of articulation of said first link.

8. A hatch cover as claimed in claim 7 in which a pawl is mounted to swivel in bearings on said first link and, in the folded position of said pair of folding covers nearer to said one end of the hatch, it engages with a stop on the sill of the hatch.

9. A hatch cover as claimed in claim 1 in which the I ratio of said first and second lever arms is about 1:2 in the extended position of said interconnected pairs of covers. j

10. A hatch cover as claimed in claim 1 in which said other cover of said adjacent covers is provided with rollers which are supported underneath a guide track attached to the sill of the hatch, in which track ends at such a distance from the articulation of the pair of folding covers nearer to said one end of the hatch that the rollers are freed from the guide track when the covers of said pair of folding covers nearer to said one end of the hatch have reached their fully folded position.

11. A hatch cover as claimed in claim 1 in which a holding-down roller working in conjunction with said other cover of said adjacent covers is provided on the sill of the hatch in the region in which said other cover lies in its closed position.

12. A hatch cover as claimed in claim 1 in which hydraulically operated bolting means are provided in the region of the folding hinge of said pair of folding covers further from said one end of the hatch which can be controlled by means of a hydraulic end switch in such a way that, during the folding and unfolding movement of the pair of folding covers nearer to said one end of the hatch, they arrest the said further pair of folding covers in the extended position and remove this arrestment when said nearer pair of covers has reached its completely folded position. v

13. A hatch cover as claimed in claim 12 in which a hydraulically-operated bolting system is provided on the said nearer pair of folding covers, which is activated by said hydraulic end switch mounted on this pair of covers in such a way that the bolting comes into action when the fully folded position is reached.

14. A hatch cover as claimed in claim 13 in which a hydraulic switch is mounted on said further pair of folding covers in such a way that it arrests the bolting of said nearer pair of folding covers in the bolted position during the folding or unfolding of said further pair of folding covers.

7 15. A hatch cover as claimed in claim 1 in which the crank is bent in its plane in such a way that it exhibits a deep indentation, opening towards the adjacent cover, between its points of. articulation.

16. A hatch cover as claimed in' claim 1, in which stopping means are provided through which a downward swivelling movement of said first link about its point of articulation to said one cover of said adjacent covers is prevented.

17. A hatch cover as claimed in claim 16 in which said stopping means are provided on said other cover of said adjacent covers to limit the relative swivelling movement between these covers and said first link in the folded-up position of the covers.

18. A hatch cover as claimed in claim 1 in which said first link is mounted on the side of said adjacent covers coaxially of the point of articulation of the crank and spaced axially therefrom.

19. A hatch cover as claimed in claim 18, in which a said first link is provided on each side of the crank and spaced axially therefrom coaxially of the point of articulation of the crank. I

20. A batch cover as claimed in claim 19 in which said first links are each mounted in an accepting pocket, open at the top, abovea seal between said adja- 

1. A hatch cover including a pair of folding covers to be articulated to the hatch adjacent one end thereof, at least one further pair of folding covers articulated to the first pair, a four-link drive mechanism interconnecting adjacent covers of adjacent pairs of said folding covers and a piston device mounted to oPerate the drive mechanism to effect swivelling between sand two adjacent covers, the drive mechanism comprising a crank engaged by said piston device and pivotally mounted on one of said adjacent covers, a first link pivotally connected between tbe crank at the point of its articulation with said one cover and the other cover of said adjacent covers, thereby to allow said adjacent covers to be swivelled through an included angle of 180* and a second link pivotally connected between said crank at a point spaced from the point of its articulation to said one cover and said other cover at a point spaced from the point of its articulation to said first link, a first lever arm of the crank between the line of action of the piston device and the point of articulation of the crank with said one cover being shorter than a second lever arm between said point of articulation of the crank with said one cover and said second link when the covers are in their fully-extended positions in which the included angle between said adjacent covers is 180*.
 2. A hatch cover as claimed in claim 1 in which means are provided on said one cover of the adjacent pair co-operable with a stationary part of the hatch to hold the pair of folding covers nearer to said one end of the hatch in its folded position, and release means are provided on said other cover of the adjacent pair to render said holding means inoperable when the other pair of said folding covers, that is the pair further from said one end of the hatch has been closed.
 3. A hatch cover as claimed in claim 2 in which a swivelling pawl is mounted on said one cover of said adjacent covers adjacent tbe point of articulation thereon of the crank and that a fixed stop is provided on the sill of the hatch, behind which fixed stop the pawl engages when the pair of folding covers nearer to said one end of the hatch has been fully folded.
 4. A hatch cover as claimed in claim 2 in which a release lever is mounted on said other cover of said adjacent covers and works in conjunction with the holding means on said one cover of said adjacent covers.
 5. A hatch cover as claimed in claim 4 in which the release lever is able to swivel in bearings and works in conjunction with a stop on the cover carrying it which limits its downward swivelling motion.
 6. A hatch cover as claimed in claim 2 in which a swivelling pawl is mounted on said one cover of said adjacent covers adjacent the point of articulation thereon of the crank which engages behind a stop mounted in a fixed position on the sill of the hatch, and a release lever is mounted on said other cover of said adjacent covers and works in conjunction with the pawl in such a way that on the closure of this cover to the end of its closure path, the pawl is brought out of its engagement with said fixed stop.
 7. A hatch cover as claimed in claim 1 in which said first link is mounted adjacent the side edes of the hatch cover, and two bogie wheels are mounted on the drive mechanism and rest on a runway on the edge of the sill of the hatch, the distance apart of said wheels being greater than the distance apart of the two points of articulation of said first link.
 8. A hatch cover as claimed in claim 7 in which a pawl is mounted to swivel in bearings on said first link and, in the folded position of said pair of folding covers nearer to said one end of the hatch, it engages with a stop on the sill of the hatch.
 9. A hatch cover as claimed in claim 1 in which the ratio of said first and second lever arms is about 1:2 in the extended position of said interconnected pairs of covers.
 10. A hatch cover as claimed in claim 1 in which said other cover of said adjacent covers is provided with rollers which are supported underneath a guide track attached to the sill of the hatch, in which track ends at such a distance from the articulation of the pair of folding covers nearer to said one end of the hatch that the rollers are freed from the guide track when the covers of said paIr of folding covers nearer to said one end of the hatch have reached their fully folded position.
 11. A hatch cover as claimed in claim 1 in which a holding-down roller working in conjunction with said other cover of said adjacent covers is provided on the sill of the hatch in the region in which said other cover lies in its closed position.
 12. A hatch cover as claimed in claim 1 in which hydraulically operated bolting means are provided in the region of the folding hinge of said pair of folding covers further from said one end of the hatch which can be controlled by means of a hydraulic end switch in such a way that, during the folding and unfolding movement of the pair of folding covers nearer to said one end of the hatch, they arrest the said further pair of folding covers in the extended position and remove this arrestment when said nearer pair of covers has reached its completely folded position.
 13. A hatch cover as claimed in claim 12 in which a hydraulically-operated bolting system is provided on the said nearer pair of folding covers, which is activated by said hydraulic end switch mounted on this pair of covers in such a way that the bolting comes into action when the fully folded position is reached.
 14. A hatch cover as claimed in claim 13 in which a hydraulic switch is mounted on said further pair of folding covers in such a way that it arrests the bolting of said nearer pair of folding covers in the bolted position during the folding or unfolding of said further pair of folding covers.
 15. A hatch cover as claimed in claim 1 in which the crank is bent in its plane in such a way that it exhibits a deep indentation, opening towards the adjacent cover, between its points of articulation.
 16. A hatch cover as claimed in claim 1, in which stopping means are provided through which a downward swivelling movement of said first link about its point of articulation to said one cover of said adjacent covers is prevented.
 17. A hatch cover as claimed in claim 16 in which said stopping means are provided on said other cover of said adjacent covers to limit the relative swivelling movement between these covers and said first link in the folded-up position of the covers.
 18. A hatch cover as claimed in claim 1 in which said first link is mounted on the side of said adjacent covers coaxially of the point of articulation of the crank and spaced axially therefrom.
 19. A hatch cover as claimed in claim 18, in which a said first link is provided on each side of the crank and spaced axially therefrom coaxially of the point of articulation of the crank.
 20. A hatch cover as claimed in claim 19 in which said first links are each mounted in an accepting pocket, open at the top, above a seal between said adjacent covers. 